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SubjectRe: kernel + gcc 4.1 = several problems
Grzegorz Kulewski wrote:
> On Wed, 3 Jan 2007, Alan wrote:
>> The proper fix for all of this mess is to fix the gcc compiler suite to
>> actually generate i686 code when told to use i686. CMOV is an optional
>> i686 extension which gcc uses without checking. In early PIV days it made
>> sense but on modern processors CMOV is so pointless the bug should be
>> fixed. At that point an i686 kernel would contain i686 instructions and
>> actually run on all i686 processors ending all the i586 pain for most
>> users and distributions.
> Could you explain why CMOV is pointless now? Are there any benchmarks
> proving that?

In theory modern processors should have no trouble converting a
test/move sequence into the same uops generated by a cmov instruction,
for one.


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